You have an older wii that has bootmii installed as boot2. Thats a very, very good thing. You should do a nand backup now if you havent already. You can rename the bootmii folder on the card to something else (or move to your PC) and you wont have this behavior anymore.
Be very happy you have a bootmii/boot2 wii tho. With a nand backup, you can restore if you mess it up in the future. In fact, I'd recommend doing an extended happy-dance.